RAILWAY CONSTRUCTION. 27 



(2) At a siding-junction in one of the following manners, 

 except where it is possible to work the traffic with the engine 

 at the lower end of a goods or mineral train, in which case an 

 undertaking (see No. 35) to do so, given by the company, will 

 be accepted as sufficient : 



(a) A similar loop to be constructed as in the case of a 



station. 



(6) Means to be provided for placing the whole train on 

 sidings clear of the main line before any shunting 

 operations are commenced. 



17. Engine- turntables of sufficient diameter to enable the 

 longest engines and tenders in use on the line to be turned 

 without being uncoupled to be erected at terminal stations and 

 at junctions and other places at which the engines require to be 

 turned, except in cases of short lines not exceeding 15 miles in 

 length, where the stations are not at a greater distance than 

 3 miles apart, and the railway company gives an undertaking 

 (see No. 35) to stop all trains at all stations. Care to be taken 

 to keep all turntables at safe distances from the adjacent lines 

 of rails, so that engines, waggons, or carriages, when being 

 turned, may not foul other lines or endanger the traffic upon 

 them. 



18. Cast-iron must not be used for railway under-bridges, 

 except in the form of arched-ribbed girders, where the material 

 is in compression. 



In a cast-iron arched bridge, or in the cast-iron girders of an 

 over-bridge, the breaking weight of the girders not to be less 

 than three times the permanent load due to the weight of the 

 superstructure, added to six times the greatest moving load that 

 can be brought upon it. 



In a wrought-iron or steel bridge, the greatest load which 

 can be brought upon it, added to the weight of the super- 

 structure, not to produce a greater strain per square inch on any 

 part of the material than five tons where wrought-iron is used, 

 or six tons and a half where steel is used. 



The engineer responsible for any steel structure to forward 

 to the Board of Trade a certificate to the effect that the steel 

 employed is either cast-steel, or steel made by some process of 

 fusion, subsequently rolled or hammered, and of a quality pos- 

 sessing considerable toughness and ductility, together with a 

 statement of all the tests to which it has been subjected. 



